The present disclosure relates to a transport system and to a system for moving transport bodies excited by permanent magnets. In particular, the present disclosure relates to an automatic braking of the transport bodies in the event of an interruption in an electrical power supply, the aim being a fixed local arrangement of the transport bodies for braking the transport body under levitation.
There are known transport systems in which the transport bodies (known as movers) are supported with almost no friction in the electromagnetic field. The controllable electromagnetic forces are used both for the drive of the transport bodies and for electromagnetic linear support or levitation over a flat, electrically excited transporting area (also referred to as an X-Y stator). Such a system is described in WO 2013/059934 A1. The present disclosure is based expressly on the subject matter disclosed therein. It goes without saying that the safety device proposed according to the disclosure can however be used for all planar motor systems comprising transport bodies with a permanent magnet. A requirement when using such a drive is that it can also be used vertically. For example, the transport bodies can make it possible to transport items to be transported on a substantially vertical wall. Similarly, an arrangement overhead is conceivable. For this purpose, it must be ensured in particular in the event of an unforeseen powerless state that the transport bodies remain in their position, which is advantageous both with regard to safety at work and with regard to maintaining states in a process during an interruption in an electrical power supply.
The drive system of the system disclosed in WO 2013/059934 A1 has permanent magnets in the transport bodies that are provided in an X-Y Halbach array. The magnetic field of these permanent magnets interacts with the magnetic field of electrical conductors in the stator, which follow a specific X-Y arrangement made to match the magnets. The interaction of the permanent-magnetic Halbach systems with the electromagnetic fields occurring in the stator as a result of the current made to flow through the conductor tracks has the effect of generating the driving forces acting on the transport bodies in the directions X and Y and also a lifting force (carrying force) in the Z direction. One challenge is to ensure that, in particular in the event of a power failure, the transport bodies are safely braked and maintain their position. This applies both to the case of a horizontal arrangement and the case of a vertical arrangement of the stator and the transport bodies, in particular if the voltage supply fails suddenly and unexpectedly. Sometimes, while they are moving, the transport bodies still have relatively great amounts of kinetic energy, which on the one hand depends on the moved (feeder) mass and on the other hand on the current speed at the moment of power failure. Due to the fact that the friction in both directions of the plane of movement (X/Y direction) is very small, the carrying bodies can under some circumstances still cover relatively long distances and cause damage to the stationary drive elements, other components of the transport system or even to persons. With the systems that are known in the prior art, the braking is performed by switching over the control to braking mode and powerless stopping for example as follows: when there is a voltage failure of the supply voltage, the kinetic energy of the transport bodies is recovered in a battery or a “super cap” in the DC link of the drive system or dissipated in a braking resistance. The braking may also be assisted/realized by using an energy buffer (uninterruptible power supply, UPS), so that active braking by means of the drive components of the transport system is possible. Without a UPS, it is not possible however to establish a safe setup of the systems that are known in the prior art.
It is an object of the present disclosure to alleviate or eliminate the aforementioned disadvantages.